Machine for forming cylindrical bales of crop
BACKGROUND OF THE INVENTION 
     This invention relates to a machine for forming cylindrical bales of crop and more particularly relates to such a machine for making bales which are of low density or &#34;soft&#34;. 
     Machines, towed by a tractor, for forming large cylindrical bales of hay (so-called &#34;round balers&#34;) are well known. As the machine advances, the crop is removed from a windrow by a pick-up mechanism and delivered rearwardly to a baling chamber where it is rolled round upon itself into a bale. 
     In one form of such a machine, the baling chamber is defined by runs of belts which move outwardly to enlarge the chamber so as to accommodate the bale as it grows in size. The belts are trained over rolls connected to a drive. A pair of rolls is located at the top of the chamber and these rolls are carried by a swingable tension arm on either side of the machine enabling the two rolls to swing upwardly as the girth of the bale increases. The tension arms are connected to hydraulic piston and cylinder units, i.e., tension cylinders, which resist their upward movement sufficiently to ensure that a dense bale is formed. Hydraulic piston and cylinder units are used to raise a rear gate of the machine to release a completed bale and these units, i. e., gate cylinders, are connected to the tension cylinders. 
     In most circumstances, a uniformly dense bale is highly desirable. However, in some conditions, it is useful for the core (or indeed the entire bale) to be of low density or soft. Such conditions occur, for example, when the crop has to be baled wet, and hot air is subsequently blown through the completed bale to reduce the excess moisture. This treatment is obviously more effective with a looser bale. Certain special applications also make a softer bale more desirable, e.g., a machine for grinding straw prior to its use in mushroom growing beds will more readily accept this type of bale. 
     The hydraulic circuitry involving the tension cylinders which brake the tension arms as referred to above includes first and second supply/return lines from quick couplers, connected to the hydraulic supply of the tractor towing the baler, to the rod ends and piston ends respectively of the cylinders. Pressure in the rod ends resists extension of the cylinders and therefore affords the braking effect on the tension arms. Thus, control of this pressure provides control of the density of the bale. 
     In the known Model 550 Round Baler, produced and marketed by Deere &amp; Company, the pressure is controlled as follows. A check valve is disposed in the first supply/return line running from one of the couplers to the rod ends, and allows flow in the direction of the rod ends. The rod and piston ends are connected by a bypass line interconnecting the first and second supply/return lines which respectively run to the rod and piston ends, with the bypass line being connected to the first supply/return line at a point downstream of the check valve. Located in the bypass line is an adjustable bale density relief valve. The setting for the opening of this latter valve, typically at 180 bars, determines the pressure at which the rod ends are relieved and hence the density of the bale being formed. U.S. Pat. No. 4,391,187 granted to Koning et al. on 5 July 1983 discloses and describes a tensioning system substantially similar to that embodied in the Model 550 Round Baler. 
     It is desirable to be able to minimize the pressure in the rod ends to produce softer bales (or cores) when needed, and yet maintain the capability of the machine to make dense bales. A simple way of achieving this has been proposed in which a valve is disposed in a line between the rod and piston ends of the tension cylinders and is selectively shiftable between an open position connecting the opposite ends of the tension cylinders to each other for effecting formation of a bale having a soft core and a closed position enabling pressure to be maintained in the rod ends for dense baling. However, the hydraulic circuitry connecting the tension cylinders and gate cylinders is such in, for example, the afore-mentioned Model 550 Round Baler (as will be explained later in detail) that, after closing the gate following release of a completed bale through the raised gate, hydraulic fluid is trapped under pressure in the rod ends of the tension and gate cylinders. This fluid flows to the piston ends to equalize the pressure at the rod and piston ends, but nevertheless, due to difference in surface areas at the ends, the gate cylinders tend toward unwanted creeping extension and thereby release latches which keep the gate closed with the result that baling cannot start until the latches have again been secured. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided a machine for forming low density or soft cylindrical bales and, more particularly, there is provided such a machine which overcomes the aforementioned difficulties associated with the prior art machine. 
     An object of the invention is to provide a machine for forming cylindrical bales of crop which includes a hydraulic system incorporating a two-way tension cylinder for resisting the expansion of an expansible bale chamber, a two-way gate cylinder for selectively retaining a gate latch in its latched position and for moving a discharge gate of the machine between open and closed positions; and a bypass valve means operable between a normal home position, wherein it prevents flow between rod and piston ends of the tension cylinder, except by way of an adjustable high pressure relief valve connected in parallel with the bypass valve means, while permitting free flow to and from the piston end of the gate cylinder, and an actuated position wherein it permits free flow between the rod and piston ends of the tension cylinder while stopping flow to the piston end of the gate cylinder, whereby a dense bale is formed when the bypass valve is in its normal position and a soft bale is formed and the gate cylinder is prevented from creeping when the bypass valve is in its actuated position. 
     A more specific object of the invention is to provide a machine, as described in the previous object, wherein the valve means is solenoid operated and when energized places the valve in its actuated position and when de-energized permits the valve to assume its home position and wherein the coil of the solenoid valve is connected in an electrical circuit including a bale size switch located so as to be opened for de-energizing the solenoid when a bale core is formed to a preselected size within the bale chamber. 
     These and other objects will become apparent from a reading of the ensuing specification together with the appended drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic, right side elevational view of a machine for forming large cylindrical bales of crop material showing certain details only and having an electrical circuit superimposed thereon. 
     FIG. 2 is a diagram of a hydraulic circuit for the machine in FIG. 1. 
     FIG. 3 is a diagram of a modified hydraulic circuit for the machine in FIG. 1. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In FIG. 1, the baler includes a main frame 10 mounted on a pair of wheels 12. The main frame has an upright fore-and-aft extending wall 14 on either side connected by transverse beams (not shown). A draft tongue 16 is connected to a transverse beam at the front of the frame 10 and extends forwardly for attaching the baler to a tractor (also not shown) which draws the machine. 
     A plurality of lateral rolls extend over the width of the machine. One set of rolls 18, 20, 22, 24, 26, 28 is journalled in the side walls 14, while another set consisting of rolls 30, 32, 34 is journalled in a swingable gate 36. There is also a pair of chamber restricting rolls 38, 40 and two belt take-up rolls 42, 44. 
     Six rubber belts 46 are trained side-by-side over the rolls, with the exception of the roll 18 which acts as a stripper roll, to provide the configuration shown and they move in the direction indicated by arrows 48, the stripper roll 18 being driven anti-clockwise as viewed in FIG. 1. However, alternate belts only are trained over the lower foremost roll 22, while the remaining belts by-pass this roll, to provide a staggered array which is of no significance in relation to the present invention but which is described in U.S. Pat. No. 4,399,746, granted 23 Aug. 1983. Upwardly extending runs 50, 52 of the belts 46 define a bale-forming chamber 54, the ends of which are provided by the side walls 14 and gate 36 and which has an inlet 56 for crop received from a pick-up 58 beneath it. 
     In order to accommodate the increasing diameter of a growing bale core in the bale-forming chamber 54, the size of the chamber must also increase and a belt take-up and tensioning mechanism is provided at either side of the machine. These mechanisms include: a pair of rearwardly extending tension arms which are mounted rigidly at the forward end of the main frame 10 on a horizontal transverse shaft 60, providing a pivot connection for the arms, and of which the right hand arm 62 only is shown; the belt take-up roll 42 which is supported at either end at an intermediate location on the arms 62; and the pair of chamber restricting rolls 38, 40 supported at the free ends of the arms. The arms are biased in an anti-clockwise direction (in FIG. 1) by a pair of springs, one on either side of the main frame 10, of which only the right hand spring 64 is shown and only its arrangement will be described, the other being similar. The spring 64 is connected at its lower end by a cable 66 which runs over a pulley 68 to a lever portion 70 of the arm 62, the portion 70 being rigid with the pivot shaft 60, and at its upper end by a cable 72 via a pulley 74 to one arm of a bell crank 76 the other arm of which bears one end of the take-up roll 44. The free end of the lever portion 70 is pivotally connected at a point 78 to the piston rod of a piston and cylinder unit or 80, loading the arm 62, of which the cylinder is in turn pivotally connected to the frame 1 at a point 82, a similar arrangement being provided also on the left hand side of the machine. 
     A further piston and cylinder unit 84 (on either side of the machine) is connected between pivot points 86, 88 on the gate 36 and main frame 10 for opening and closing the gate. For convenience the units 84 will be referred to as gate cylinders 84, and the units 80 as tension cylinders 80. 
     The arrangement of the relevant hydraulic circuit will now be described. In FIG. 2, the hydraulic circuit is seen to include a direction control valve 90, a pump 91 and a sump 92 all of which would normally be found on a towing tractor. A first supply/return line 94 is connected to the direction control valve 90 and is branched with one part being connected directly to the rod ends of the gate cylinders 84 and with another part containing a check valve 96 and being connected to the rod ends of the tension cylinders 80. A second supply/ return line 98 is connected to the direction control valve 90 and is branched with one branch being connected directly to the piston ends of the tension cylinders 80 and with another branch being connected to the piston ends of the gate cylinders 84 by way of a bypass valve 100 (in the form of a three-way, two-position, solenoid actuated valve) and a manually operable gate lock valve -02 that is connected in series with the valve 100. A shunt line 103 connects the supply/return line 98 to the piston ends of the gate cylinders 84 by a path which circumvents the bypass valve 100, the line 103 containing a one-way valve 104 which permits flow only in a direction away from the piston ends of the cylinders. The bypass valve 100 is also connected in a bypass line 106 which interconnects the supply/return lines 94 and 98 at a location for establishing a connection between the rod and piston ends of the tension cylinders 80 in parallel with the connection thereof through a second bypass line 107 containing an adjustable high pressure relief valve 108. The flow through the bypass line 106 is restricted to a low value relative to the rest of the hydraulic circuit by sizing the line 106 accordingly or by way of an orifice (not shown) in order to ensure an appropriately substantial pressure drop between the ends of the gate cylinders 84 during closure of the gate 36. 
     Control of the solenoid of the valve 100 is exercised through an electrical circuit 110 which is shown in FIG. 1 and in which: the solenoid (i.e. the solenoid winding) of the valve 100, an automatic bale size switch 112 adjacent the tension arm 62 on the baling machine, and a manual control switch 114 on a monitor box 116 in the driver&#39;s cab of the tractor are all disposed in series with an electrical source 118 on the tractor. 
     Thus, with both the switch 112 and the switch 114 closed, the solenoid of the valve 100 will be actuated to move the valve 100 to its position connecting the rod and piston ends of the tension cylinders 80, and if either one or both of the switches is (are) open the circuit to the solenoid is broken and the valve 100 will revert to its home position shown in FIG. 2 connecting the piston ends of the gate and tension cylinders 80, 84 to each other. 
     The switch 112 operates in dependence on the position of the tension arm 62 during its swing. In particular, a short trigger arm 120 which is rigid with the transverse shaft 60 and which therefore swings with the tension arm 62 opens the switch 112 from its &#34;home&#34; closed condition when the tension arm 62 has swung to the necessary predetermined angle. The trigger arm 120 and the switch 112 are relatively adjustable so that this angle can be varied according to the choice of the operator for the core size of the bale. The switch 114 in the monitor box 116 incorporates a signal light which is &#34;on&#34; when circuit 110 is made. 
     The operation of the hydraulic circuit will now be described. 
     The control valve 100 is shown with the solenoid not actuated in a position allowing fluid flow between the piston ends of the gate and tension cylinders 84, 80, the switch 114 being open. With the valve 100 in this position, flow between the rod and piston ends of the tension cylinders will be prevented except by way of the adjustable relief valve 108 and a dense bale will be formed. Specifically, the adjustable relief valve 108 is set, for example, at 180 bars at which pressure it will interconnect the rod and piston ends of the tension cylinders 80 with no return flow through the valve 96. In this manner, the tension cylinders 80 offer sufficiently high resistance to the upward swinging movement of the tension arms 62 and thus to the expansion of the bale chamber 54 for a dense bale to be formed. 
     If a soft core bale is required, then at the start of baling the solenoid of the valve 100 must be actuated to bring the valve into the position interconnecting the rod and piston ends of the tension cylinders 80. This is accomplished by the operator closing the switch 114 in his monitor 116. Thus, the tension cylinders 80 will not resist the movement of the tension arms 62 and a soft core will be baled. 
     At the chosen size of core, the tension arm 62 reaches the predetermined angle necessary for the trigger arm 120 to open the bale size switch 112, thus breaking circuit 110 which ceases to actuate the solenoid of the valve 100 causing the valve to revert to its normal home position preventing circuit flow between the rod and piston ends of the tension cylinders 80. With the valve in this position, control of the pressure in the rod ends of the tension cylinders 80 is again by way of the high pressure relief valve 108 and the density of the outer bale portion being produced is high. 
     Should the driver wish to produce a completely soft bale, the circuit 110 must be maintained as made during the entire operation. He therefore closes the control switch 114 initially as before, but adjusts the relative positions of the trigger arm 120 and the bale size switch 112 so that the arm cannot open the switch 112 throughout the entire period of formation of the complete bale. 
     The relationship of the positions of the valve 100 to the gate cylinders will now be described. With the valve 100 in its home (non-actuated) position, the connection between the rod and piston ends of the tension cylinders 80 is closed and the piston ends of the tension and gate cylinders 80, 84 are interconnected with the supply/return line 98. Most importantly, when the valve 100 is in its actuated position in which the rod and piston ends of the tension cylinders 80 are connected, flow through the valve 100 to the piston ends of the gate cylinders 84 is stopped although flow from the latter to the supply/return line 98 is still possible through the check valve 104. 
     Such an arrangement overcomes the following problem. If a valve is provided between the ends of the tension cylinders 80 merely to open in order to connect those ends or close to cut the connection, difficulties arise with the gate cylinders 84. When the gate 36 is closed by flow to the rod ends of the gate cylinders 84, as occasioned by shifting the control valve 90 to connect the pump 91 to line 94 after release from the baler of a completed bale, and as the valve 90 is brought to neutral, oil under pressure trapped in the rod side of the cylinders will continue to flow through this valve to the piston sides of the cylinders 80, 84. The pressure will equalize at both ends of these cylinders but this will cause the gate cylinders 84 to tend to extend. The tension cylinders 80 are not affected in the same way, since the tension arms 62 offer sufficient resistance to creeping extension. On the other hand, the only resistance to the initial extension of the gate cylinders 84 is provided by very easily opened gate latches. Thus, the gate 36 will tend to be released from these latches and in these circumstances baling will not then be possible. 
     Since, as mentioned above, when the present valve 100 connects the ends of the tension cylinders 80, flow to the piston ends of the gate cylinders 84 is nevertheless stopped and unwanted extension of these cylinders is avoided. It is also possible to close the gate 36 when the valve 100 is in its actuated position because fluid can flow, as also explained above, through the check valve 104 and the control valve 90, to the sump 92 on the tractor from the piston ends of the gate cylinders 84. Internal leakage of the valve 100 should be very low when it is in its home position to maintain pressure for high density baling. 
     Instead of using a single two-position by-pass valve 100 as in FIGS. 1 and 2, two two-way, two-position, solenoid actuated valves 122, 124 can be employed as shown in FIG. 3. The valve 122 which is normally closed is disposed between the ends of the tension cylinders 80, and the valve 124 which is normally open is between the piston ends of the tension cylinders 80 and the piston ends of the gate cylinders 84. The combined positions of the valves 122, 124 in FIG. 3 correspond to the home position of the valve 100 illustrated in FIG. 2, i.e. the solenoids of the valves 122, 124 are not actuated. Thus the valve 124 is in its free flow position, while the valve 122 cuts the connection between the ends of the tension cylinders 80. The valve 122 will be moved on actuation to a free flow position and the valve 124 to a position cutting flow to the piston ends of the gate cylinders 84 corresponding to the actuated position of the valve 100. A check valve 126 in FIG. 3 incorporated in the valve 124 corresponds to the check valve 104 in FIG. 2. Thus, the function of the valves 122, 124 taken together is the same as that of the valve 100.